Jeremiah 17:10 says “I, YHVH, search the mind, I try the heart, even to give every man according to his ways, according to the fruit of his doings.”  So we clearly see that God does search our hearts for sincerity and tests our will for resolve to be quick to serve Him without ulterior motive… Like Abraham who it is said was always quick to obey and never thought negative or grumbled in his heart… A great example for us!